This invention relates to methods for preparing .alpha.-substituted styrenes. .alpha.-(1-haloalkyl)styrenes are taught in U.S. Pat. No. 3,391,203 to be useful as parasiticides and insecticides. They are also known to be useful intermediates in the manufacture of other biologically-active compounds such as herbicides, as taught in U.S. Pat. No. 3,373,011. In preparing .alpha.-substituted styrenes, U.S. Pat. No. 4,188,346 discloses that the Lewis acid SbCl.sub.5 alone was a good catalyst, but it was later shown to be difficult to remove and detrimental to subsequent epoxidations. U.S. Pat. No. 4,205,015 discloses a method for preparing .alpha.-substituted styrenes using a catalyst such as AlCl.sub.3 deposited on an inert support such as silica gel or alumina. However, this catalyst suffers the shortcomings of requiring additional time and expense to prepare the catalyst, and has noxious fumes safety problems associated with undesirably high levels of noxious fumes such as hydrogen halide.
In view of the deficiencies of prior art methods, it would be highly desirable to provide an improved method for making .alpha.-substituted styrenes.